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Richard Stallman et le logiciel libre
19 octobre 2011, par
Mis à jour : Mai 2013
Langue : français
Type : Texte
Autres articles (24)
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MediaSPIP Core : La Configuration
9 novembre 2010, parMediaSPIP Core fournit par défaut trois pages différentes de configuration (ces pages utilisent le plugin de configuration CFG pour fonctionner) : une page spécifique à la configuration générale du squelettes ; une page spécifique à la configuration de la page d’accueil du site ; une page spécifique à la configuration des secteurs ;
Il fournit également une page supplémentaire qui n’apparait que lorsque certains plugins sont activés permettant de contrôler l’affichage et les fonctionnalités spécifiques (...) -
Les tâches Cron régulières de la ferme
1er décembre 2010, parLa gestion de la ferme passe par l’exécution à intervalle régulier de plusieurs tâches répétitives dites Cron.
Le super Cron (gestion_mutu_super_cron)
Cette tâche, planifiée chaque minute, a pour simple effet d’appeler le Cron de l’ensemble des instances de la mutualisation régulièrement. Couplée avec un Cron système sur le site central de la mutualisation, cela permet de simplement générer des visites régulières sur les différents sites et éviter que les tâches des sites peu visités soient trop (...) -
Use, discuss, criticize
13 avril 2011, parTalk to people directly involved in MediaSPIP’s development, or to people around you who could use MediaSPIP to share, enhance or develop their creative projects.
The bigger the community, the more MediaSPIP’s potential will be explored and the faster the software will evolve.
A discussion list is available for all exchanges between users.
Sur d’autres sites (4101)
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avfilter/vf_fps : extend support for expressions
24 février 2021, par James Almeravfilter/vf_fps : extend support for expressions
AV_OPT_TYPE_VIDEO_RATE AVOption types are parsed as expressions, but in a
limited way. For example, name constants can only be parsed alone and not as
part of a longer expression.This change allows usage like
ffmpeg -i IN -vf fps="if(eq(source_fps\,film)\,ntsc_film\,source_fps)" OUT
Suggested-by : ffmpeg@fb.com
Signed-off-by : James Almer <jamrial@gmail.com> -
FFmpeg subtitle filter set start time
31 décembre 2020, par CasualDemonI am trying to burn-in subtitles for a shorter section of a video, but using the subtitles filter always starts from the beginning of the subtitle stream, not at the specified start time, even when copying from the same video.


So for example if I start an encode 10 minutes in to a film, the video will properly be set from there, but the subtitles will start from the beginning (10 minute offset in this case).


ffmpeg -y -ss 600.0 -to 660.0 -i movie.mkv -filter_complex "[0:0]subtitles='movie.mkv':si=1[v]" -map "[v]" -c:v libx265 -crf 22 output.mkv


This is not a problem when using picture based subtitles and the overlay filter, such as :


-filter_complex "[0:0][0:2]overlay[v]"


It seems to only affect text based subtitles. I don't know if this is just not possible and will require another solution, or if I am approaching it wrong. Any help is appreciated !


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FFmpeg - generate x264 CBR video transport stream with C-API
6 juillet 2020, par ZeroDefectUsing various posts sprinkled around the Internet, including this one here on SO, I've been able to understand how to use the FFmpeg cli to generate a CBR video bitrate using the x264 codec (wrapped in an MPEG-2 transport stream). Note : I'm concerned with the video bitrate - nothing else.


ffmpeg -i cbr_test_file_input.mp4 -c:v libx264 -pix_fmt yuv420p -b:v 6000000 -preset fast -tune film -g 25 -x264-params vbv-maxrate=6000:vbv-bufsize=6000:force-cfr=1:nal-hrd=cbr -flags +ildct+ilme x264_cbr_test_output.ts


However, I'm trying to approach this from an FFmpeg C-API point of view. I'm having issues. I've knocked together some code to try do something very similar to what is being done in the FFmpeg CLI. I can generate a transport stream of what I think should be CBR, but the profile of the video bitrate is very different from what I thought was the FFmpeg cli equivalent :


The initialisation of the AVCodecContext looks something like :


av_dict_set(&pDict, "preset", "faster", 0);
 av_dict_set(&pDict, "tune", "film", 0);
 av_dict_set_int(&pDict, "rc-lookahead", 25, 0);

 pCdcCtxOut->width = pCdcCtxIn->width;
 pCdcCtxOut->height = pCdcCtxIn->height;
 pCdcCtxOut->pix_fmt = AV_PIX_FMT_YUV420P;
 pCdcCtxOut->gop_size = 25;

 // Going for 6Mbit/s
 pCdcCtxOut->bit_rate = 6000000;
 //pCdcCtxOut->rc_min_rate = pCdcCtxOut->bit_rate;
 pCdcCtxOut->rc_max_rate = pCdcCtxOut->bit_rate;
 pCdcCtxOut->rc_buffer_size = pCdcCtxOut->bit_rate;
 pCdcCtxOut->rc_initial_buffer_occupancy = static_cast<int>((pCdcCtxOut->bit_rate * 9) / 10);

 std::string strParams = "vbv-maxrate="
 + std::to_string(pCdcCtxOut->bit_rate / 1000)
 + ":vbv-bufsize="
 + std::to_string(pCdcCtxOut->bit_rate / 1000)
 + ":force-cfr=1:nal-hrd=cbr";

 av_dict_set(&pDict, "x264-params", strParams.c_str(), 0);

 pCdcCtxOut->field_order = AV_FIELD_TT;
 pCdcCtxOut->flags = (AV_CODEC_FLAG_INTERLACED_DCT | AV_CODEC_FLAG_INTERLACED_ME | AV_CODEC_FLAG_CLOSED_GOP);

 // WARN: Make some assumptions here!
 pCdcCtxOut->time_base = AVRational{1,25};
 pCdcCtxOut->framerate = AVRational{25,1};
 pCdcCtxOut->sample_aspect_ratio = AVRational{64,45};
</int>

The output graphs appear very different :




Above is the FFmpeg CLI output - video bitrate holds fairly steady.




Above is the output of my sample application - some significant dips in the video bitrate.


I've taken this a step further and created a git repo consisting of :


- 

- Code of sample application
- Test input file (.mp4)
- Outputs (.ts file) of tests
- Graphs of output bitrates.










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